1. Field of the Invention
The present invention relates to a process for producing benzyl acetate and benzyl alcohol.
Benzyl acetate itself is useful as a solvent and a perfume. Benzyl alcohol which is derived from the benzyl acetate by hydrolysis or by transesterification with methanol is an important compound useful as a powerful solvent, a nontoxic medical additive, and an intermediate compound for agricultural chemicals and medicines.
2. Description of the Related Art
For industrial production of benzyl acetate, a process is known in which benzyl chloride produced by chlorination of toluene is hydrolyzed by alkali, and the resulting benzyl alcohol is esterified with acetic acid. This process comprises multistage reactions, and includes many steps of separation and purification after the respective reactions. Therefore, the process is complex and is not advantageous economically. Moreover, in the hydrolysis reaction of the second step, an alkali such as sodium hydroxide is required in an equivalent amount or more, and a large amount of a salt containing organic compounds is formed as the by-product, which involves problems in after-treatment thereof.
In a process not industrially conducted, benzyl acetate is produced by reaction of toluene, acetic acid, and oxygen in the presence of a catalyst for oxyacetoxylation. This process produces benzyl acetate in one step reaction without formation of a by-product salt, so that it is advantageous economically and can be of low environmental load.
Many techniques of benzyl acetate production have been disclosed, for example, in JP-B-42-13081, JP-A-52-151135, JP-A-52-151136, JP-B-50-28947, JP-B-52-16101, and JP-A-63-174950 (The term "JP-A" herein means an "unexamined published Japanese patent application", and the term "JP-B" herein means an "examined Japanese patent publication"). However, in these techniques, detailed studies are not made on industrial production process including separation and purification of benzyl acetate. Therefore, known techniques are not satisfactory for production of high-purity benzyl acetate.
On the other hand, benzyl alcohol can be produced by the known processes below. Of these, the processes (1) and (3) are practiced industrially:
(1) Hydrolysis of benzyl chloride by sodium hydroxide, PA1 (2) Hydrolysis of benzyl acetate in the presence of a catalyst, and PA1 (3) Reduction of benzaldehyde by hydrogen in the presence of a catalyst.
The above processes (1) and (2) both produces benzyl alcohol by hydrolysis. The process (1) consumes an equivalent amount or more of sodium hydroxide for stoichiometric reaction of benzyl chloride, involving a problem of after-treatment of a large amount of an aqueous solution of organic compound-containing sodium chloride formed as a by-product. The process (3) employs relatively expensive benzaldehyde as the starting material, and is disadvantageous economically.
The process (2) of hydrolysis of benzyl acetate to produce benzyl alcohol forms useful acetic acid as the by-product without discharging waste water, thus being economical and of low environmental load.
Regarding this hydrolysis process, a method is disclosed in which a mixture of water and benzyl acetate in a volume ratio of water/benzyl acetate of 25 is hydrolyzed at a temperature of 20-30.degree. C. in the presence of Amberlite IR-100, a sulfonic acid type cation-exchange resin (J. Chem. Soc., No.5, 1952, 1607). However, in this process, the catalyst activity is low, and an extremely large amount of water is required, so that the starting material concentration is lowered. Therefore, this process is not industrially advantageous in consideration of the energy for removal of unreacted water from the liquid reaction mixture. Further, the above disclosure does not specifically disclose the method for isolation and purification of the resulting benzyl alcohol.
In another process (Russian Patent: SU1077875), benzyl alcohol of high purity (98%) is obtained at an improved yield by hydrolysis of benzyl acetate in a flow system at a temperature of 90-98.degree. C. at water/benzyl acetate ratio of 3 (by weight) through a porous sulfonic acid type cation-exchange resin containing 2.2-4.0 m-equivalent/g of nitro group by replacing acetic acid with water during the reaction. However, this process, which requires use of a special nitro group-containing resin as the catalyst, is not practical as an industrial process in view of the catalyst cost.
As discussed above, the benzyl alcohol production process has not yet been investigated sufficiently for industrialization including the separation and purification steps, and no process is satisfactory as the process for producing high-purity benzyl alcohol.